Note: Descriptions are shown in the official language in which they were submitted.
INTEGRAL PUMP HOUSI~G
Field of the Invention
This invention relate.s to improvements irl
aluminum die casting, more ~articularly to such die
~astillgs used for pump housincJs and other
applicalions where an inte~ral h.ard workinc~ surface
is advantageous.
Backqround of the Invention
~ luminum die castings have been used for
equipment housings for many years. The man~
advantageous mechanical properties of aluminum die
castincJs llave motivated widespread usage of sucll die
castings for pump housings. In the past, it has been
found necessary to use a separate F~ressure vessel,
preferably steel, within the housing to serve as a
~ cylinder for the pi.ston of such pumps due to the
perceived poor wear characteristics and porosity of
aluminllm.
In addition, other ~arts and subassemblies
were often present wi.th the consecluent increase ir
cost and complexity.
~ n one aspect of the present irlvention, it
has been found possible to eliminate separate ~arts
such as the pressure vessel in s~ch assemblies while
at the salne l.ime achievinc~ imProved wear
characteristics over convelltional or "so~t alulnillurn,
sucll as, ~or example type 3~0-
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CA 02021~43 1998-06-2~
The present invention accomplishes this by utilizing the
relatively hard but thin surface region or skin of approximately
0.015 to 0.030 inches depth which appertains to aluminum die
casting. In the past, such a skin was typically machined away
leaving only the soft (and possibly porous) bulk aluminum which is
unacceptable as a working surface. In the present invention, the
workpiece is die cast to near net shape and subsequently only
finish machined such that a portion of the hard surface region
remains in the aluminum and is available as a hard working surface
10 having a desired configuration and surface finish. An additional
or side benefit of this invention is that, by leaving a portion of
the hard skin on the die casting, the characteristic lower porosity
of the skin can be utilized as well.
It is believed that the mechanical properties of die
15 castings are directly related to solidification rate. The aluminum
alloy composition can be used to vary the hardness and
machinability; the cooling rate and injection pressure can a]so be
controlled to regulate surface hardness of the die casting;
entrapped gases can also affect hardness. The microstructural
20 features that affect hardness in such die castings are: i) grain
size and shape, ii) dendrite-arm spacing, and iii) the size and
distribution of second-phase particles and inclusions.
Another aspect of the present invention is the
utilization of portions of the equipment or pump housing to replace
25 discrete parts from prior art assemblies. More specifically, in
the practice of the present invention, a pressure control valve
housing, fluid return path, and stop for the pressure control valve
are preferably cast integral with the
X
~2~5 ~3
~ r~ housillcJ. In acl~ition, a valve seat may be
lo~me(l i.l~ec]Jal ~Jitll the pump llousjnrJ by machirlill~J
('oi lli.llC3 a conical sur~ace i.n tl-le housil-~c].
~ri~f_Desçription of the Drawinqs
Figure 1 is an explodecl view of selected
~arts of a prior art pump assemkly.
Figure 2 is a fragmentary side elevation
view of the pump housing of the present invention in.
assembly with parts cut away, sectioned vertically
alorlc3 a central a~is of the assembly
Figure 3 is an end elevation view of the
pump housiny of Figure 2 witll parts omitted.
Fi.yure 4 is a view similar to that of Figure
showing the llousing in an as-cast condition.
Figure 5 is an enlarged fragmenta.ry view
taken from area 5 of Figure 4.
Figure 6 is a view similar to that of Figure
5 showing the same detail after machining.
Figure 7 is an enlarc3ed fragmentary view
taken from the area 7 in Figure 2.
Figure B is a fragmentary perspective detail
of part of the assembly of Figure 2.
Detailed DescriPtion
~ eferrinc3 more particularly to Figure 1, in
the prior art, a pump assembly 10 preferably included
an aluminum die cast housing 12 containing a number
of additional parts to form a hydraulic pump
operatinc3 from an electric motor 14 secured to
llousing 12.
Assembly 10 includes a motor sl-laft 16
driving an eccentric lB secured to shaft lG b~ Jey
20. Shaft 16 rotates in a ball or roller bearing 22
with respect to housing 12. ~ccentric lB rotates in
a bearing 24 operating to drive a piston 26 upward
~' f
20213 43
aJol-lg a~is A in a pressure vessel 2~. ~ .,prill~ 30
drives agaillst a wasller 32 held on p;,stotl 2G by a
reta:irlirlg ring 34. A shaft seal 36 is prefera~l~
].ocate(l adi.lcellt bearing 22. A retaining rinc] 3~
.secures eccentric 2~ from axial movement along shaft
16.
Il, is to be understood that eccentric 1~ is
preferab],~ press-fit to the inner race 25 of bearing
~9.
Pressure vessel 28 is sealed against housing
12 by an O-rincJ 40. An oi.l pick up tube 42 is
coupled along a~is B via O-rings 44 to elbow 46.
Elbow 4G is received in pressure vessel 2~ along a
radial aperture whose a~is intersects a~is A.
An oil return tube 48 is coupled via a
plastic barbed fitting 50 along a~is C to a
rectangular projection 52 on pressure vessel 2~.
Rectangular projection 52 has a threaded bore 54
wllich receives a pressure valve housing 5G along aY~is
r~. Housing 5G encloses a needle valve assembly
having a stem 58. Stem 58 xeceives a knob 60 along
axis eY.tensiorl D'. A plastic stop G2 is preferably
interposed between valve housing 56 and knob 60.
Stop G2 has a hexagonal-sllaped bore to mate with
housing 5G and an e~ternal projection 64 whi.ch is
engageable with an internal pxojection GG on knob 50
to limit the rotation of stem 5~ to less tharl 360~.
A nylon diaphragm as.,embl~ 70 rests above
pressure ves5el 28 and fle~es in, response to
reciprocation of piston 2G. DiaphracJm 72 of assembly
70 provides a pum~ing action to a paint pump assembl~
(not shown).
P~eferring now more particularly also to
Figure 2, in the present invention, although a number
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~021543
o~ tlle operatin~ parts from tlle prior art assembly of
.gure :l, are ut;.lize~ is ~:o be noted tllat ~lle
J)re.ssllre vessel Z~, pressure valve housincJ 5G, alld
sl:op fi2 llave beell elirninated, calong wi~h a number oE
~cldltiollal parts, resulting i.n substantial cost
savlrlc~s -
In the practice of this inventioll, a
~edes;,c~ned aluminum die cast housinc] 30 is preferably
formed o~ t~pe 380 aluminum alld machined to the
configuration shown in FicJures 2 and 3.
~ rhe di.aphrac]m assembly (whicll is common to
the embodiments of Figure l and 2) irlcllldes diaphragm
7~ preferably formed of nylon. A c~lindrical spacer
block 32 has a plurality of througll holes ~4 to
permit oil to reach membrane 72. ~lock 82 also
~referably has channels 36 to permit delivery of oil
from chamber 8P to holes 84. Spring 90 acti,ng
betweell block 82 and nut 92 urc]e membrane 72 against
the top of blocl~ 82. Oil is supplied from sump Y~
throuc3h oil supply tube 96, barbed fitting S0' and
passac3eway 98 through aperture 100 to chamber ~.
Passageway 9~ is preferably formed of two
segments, 102, 104. Segment lOZ is preferably cast
in housing ~0 and segment lO~ is preferably formed by
drilling housing 30 along aY~is E. ~ pin 106 is
inserted, in segment 104 to seal passageway 9P, against
the environment e~terior of housing ~0
Referring now also to Fic3ure 2, a pressure
valve lO~ includes a needle llO press-fit and secured
into a c3enerally scluare cross section carrier ll~.
Meedle llO preferably has a cone-shaped t;.p llq
havirlc3 an included angle preferably hetween 30 a
31~. ~s rnay be seen rnore clearly in Figure 7,
--5--
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~û21~3
llou;i~ n~ i..s (~ri~Jed ~:o pro~icle passage~ay 116 alld
e~fe~:cll~ly coilled to provide cone-sllaped sectiol~
I)avitl~J all i.ncluded arlgle preferably betweerl 31 ancl
33~. llo~,:irl(3 ~0 i.s also preferably threaded to
receive valve body 120 rota~,able via valve stem 58.
spriny 122 resiliently urges needle 110 against
cone-shaped section 118.
Referrillg now also to Fic~ure 8, a stop 12
is preferably cast integral witll housing 30,
eliminatinc] the need for a separate stop 62.
~ eferring now to Fi~ure a,, housirlcJ ~0 is
sllown irl the as-cast condition. It is to be
understood that Figure 4 is sectioned at Ille same
plalle as Figu.re 2.
Referring also to Figure 5, housing ~0 is an
alurninl.lm die casting of the type h.aving a regiorl of
illcreased hardness extending a minimum de~th 126
l)elow a surface 12B of die casting ~0 as cast.
Casting ~0 is machined to a depth 130 less than the
minimum depth 1~6 of the increased hardness region
13Z to form a hard working surface 134 on die casting
80 to a desired configuration and surface finish. In
the region shown in Figures 5 and 6, it is to be
understood that a double core is used in the die
casting process with a parting line 136 separating
the cores. ~ach core is tapered in the fornl of a
truncated cone with the dial-neter increasing as
distance progresses away frorn partincJ line 136. This
results in a region of increased hardness generally
J-orming a cylindrical region surroundill~.3 a bore 13
cast in the die casting or wor]~piece ~0. In the
configurcltion shown in Figures 4 and. 5, the
cylindrical region 140 has a slight hourglass taper.
The minimum depth 126 of increased hardl-less is i.n the
2~5~3
ral~ye o~ 0.010 to 0.040 inclles as measurecl nornlal or
r,~erPerldicular to surface 1~8 o~ the die casting 80.
Tlle (Jie casti,llcJ 80, as has been said, is prefera~ly
rormed o~ type 3~0 aluminum, however, other rnaterials
~nay be ut;.lized wlli.cll will result in an increased
llardlless regioll 132.
It rnay thus be seen that an integral
cylinder liner 142 is formed with housing ~0 wherein
the alumillum die casting 80 has an as-cast ~ore
radius surroundi.ng by a generally cylindrical reyion
132 of increased hardness of a predetermined minlj.mum
depth 126 from a surface lZ~ of bore 138 and macllined
to a fillished radius slic]h~ly lar~er tllan the as--cast
bore radius whereill the finj.shed radius is less than
the sum of the as-cast bore radius and the rninilnllm
de~th 126 such tllat the integral finished cylinder
liner 142 is formed in die casting 80 at the finislled
r;.ldius arld has an increase~ surface hardness wit,J-)
respect to interior hardness of die castinc] 80 in
region 144. It is to be understood that with respect
to Figure 6, that if it is not necessary that a
surface of increased hardness eY~tend fully alony the
entire cylinder wall, that depth 130 may actually be
rlegative inasmuch as macllining may remove all of the
region 132 in th~ vicinity of parting line 136 wllile
still retaini,ny a reyion of increased hardness 132
remot,e from the vicinity of parting line 136. ~ucll a
configuration would, in ef~ect, resttlt in two band~,
of increased llardness separated by a regi.on lacl~iny
SllCIl increased hardness and ;.s believed t,o be
adeguate fsr the functioniny of p~oviding a hard
~orking surface ac]ainst which piston 26 may operate,
In such a circumstance, it is to be understood that
the porosity of castiny 80 must be carefully
, .
2~21543
(-,ollt ro~ ](~d ~ o elirn;.llate .s~e~ cle 0! I.ealrcl9~ e
vi i.~ y ~,L pa~ i.lle 13G. Cast:illJ ~0 Incly be Illade
ilnl,)e~ r; ~ O uiJ. le~.ll a(~e bY atly orle o~ a llulllber 01~
,OIIve~rltioll~1. teclllliclues, .~;uc:h as resin ilnr)rec31latioll.
I'efer~ cJ to ~ ure 4 it is furtller to l~e
~Inderstood thal a sinyle conical taper for bore 13~
may be advanta~eous in certaj.n applications of tllis
invelltio~ wllile in the con~igurltion as sllown. j.rl
~iqure 4 it ;.s preferred that bore 138 has a double
coni.cal taper as cast. It is further to be
ullderstood that in machininc~ bore 133 to arrive at
tlle conJ ic3urati.on showl-l in Fi~Jure 2, that l-.lle
integral finished cylinder liner 142 ~Jill preferably
be a riyht circula~ cylirlder.
In operation piston 2G moves upward past
aperture 100 closing off chamber ~3 causinc3 oil to
e~ert pressure on membranQ 7~ whicll will ~1e~ aCtill~
as a pumpinc~ element and liquid seal betweel-l tlle
hydraulic pump shown herein and a separate paint pulnp
(1101: ShOWII). At the same time the oil pressure will
unseat needle 110 from seat 118 regulatiny the oil
pressure in chamlJer ~8 by the action of sprinc3 122
whose force is set by the a~rial position of valve
body 120 positionable ~ia knob G0. Oil whicil leaks
past needle 110 is returned to surnp 94 vja passa~eway
].lG and fluid return path 14~.
It may thlls be seen that a norl-isotropic
llardness inteyral aluminum pairlt sprayor l~ydral).l;.c
pump sylinder and housiny may be foJ:med ~rorn a
homocleneous clie cast alumirlulllllourirlc] ~0 ha-~illc~ a
llouryJass-tapered bore 13~ ca t tl-iereirl witll t;lle bore
13~ surrounded by a circurnfererltial l-lourylass-tapered
re~ion ].32 of increased hardness witll respect to a
2~2~;43
b~ t:erior llardlless of said hOIIS; I19 at regi,on 1~
witll tlle bore rnachilled to a rigllt c;,rcular
~,yl:indric..l]. corlfic~ atiorl while remaillillc3 withill tlle
~ircllinfererl~ia], :increased llardl-less regioll 132.
:tt i.s furtllér to be understood that in tlle
practice~ of tilis inventi,orl, a one-~iece pulllp housirlq
ma~ bè formecl by housing ~0, a hydraulic piston pump
cylinder 142 cast integral with the l?um!? housing 8l)
and furthermore includiny a pressure controlled valve
housillg region 14G also cast inteqral witll the pump
housinc3 80. The fluid return path 148 is also
~referabl~ cast integral with pump housing 80 with
~ath 148 e~tending from the valve housirlg 146 towards
a fluid sump 94,. The housing 80 furthermore
preferably has a pressure control valve stop 1~4 cast
integral with pump housing 80.
Referring to Fi.gllres 3 and 4, chamber 88 i,s
preferabl~ surrounded by a recJiorl 150 whicl-l comprises
a pressure vessel inteqral with housinq 80.
It is also to be understood that valve
housing 146 preferabl~ further includes cone-shaped
section 118 coined in housing 80 to form a valve seat
integral with pump housinc3 ~0.
The invention is not to be taken as limited to
all of the details thereof as modifications and
irnprovements may be made while remaining within the
spirit and scope of the inventioll as claimed.
_y _ ,
